在扉页的南中心画一个4cm的矩形？

Question

我需要更新自定义 Beamer 主题，并且需要在标题页底部绘制一个矩形。主题是发表在 Overleaf 上如果你想玩它的话。

目前的标题页大致如下：

Beamer 模板title page目前定义如下：

% Title page - The first page of the presentation
\defbeamertemplate*{title page}{ec}[1][]
{
    \begin{beamercolorbox}[wd=\paperwidth]{titlepage}
        \begin{tikzpicture}[remember picture, overlay]
            \coordinate (SW) at (current page.south west);
            \coordinate (SE) at (current page.south east);
            \coordinate (NW) at (current page.north west);
            \coordinate (NE) at (current page.north east);

            \fill[color=ecmain,anchor=south west] (SW) rectangle (13,2.4);
            \fill[color=ecaccentyellow] (1,-6) rectangle (1.05, 1);

            \node[ecaccentyellow,anchor=north west,font=\LARGE] (title) at (1,1) {
                \inserttitle
            };
            \node[ecaccentyellow,anchor=north west,font=\Large] (subtitle) at (1,0) {
                \insertsubtitle
            };
            \node[white,anchor=south east,align=right] (author) at (12.5,-5.5) {
                \texttt{\insertauthor}\\\texttt{\insertinstitute}\\\texttt{\insertdate}
            };
            % \useasboundingbox (SW) rectangle (NE);
            % \draw [help lines] (SW) grid (NE);
        \end{tikzpicture}

        \begin{tikzpicture}[remember picture, overlay]
            \node[anchor=north] at (current page.north) {
                \includegraphics[trim=0 0 0 3mm,scale=0.25]{logo-ce-en}
            };
        \end{tikzpicture}
    \end{beamercolorbox}

    \setcounter{framenumber}{0}
}

我想在该页底部添加一个矩形。该矩形需要宽 4 厘米、高 1 厘米，并完全位于底部中央，因此标题页将如下所示：

我尝试使用 做了很多事情\draw，但无法正确地完成。

您对此有什么建议吗？